PCB units have been generally manufactured one by one. However, in recent years, in order to improve the productivity and yield in an automatic part mounting process, a plurality of PCB units having an identical pattern to each other have been printed on a single board and separated as a single unit after the part mounting process.
Such a board on which a plurality of PCBs are printed is called an arrayed PCB panel or simply a PCB panel and is classified into a 2-array PCB panel, a 3-array PCB panel, a 4-array PCB panel and the like according to the number of PCB units arrayed on the panel.
The PCB panel is designed such that each of the PCB units formed thereon is inspected on the defectiveness (before mounting part). When it is determined that at least one PCB unit is defective, the PCB panel is called an X-out PCB or an X-out board. The PCB panel determined as the X-out PCB has come into disuse. However, in recent years, a technique for replacing the defective PCB unit with a nondefective PCB unit, a process of which is called an X-out replacing process has been developed.
The X-out replacing process will be described hereinafter.
First, an electric current flow defectiveness, a surface scratch, a pattern dislocation, and the like are checked through an electric current flow test and a visual test using a magnifier with an enlargement scale of 5× or 10×, and the PCB units on the PCB panel, which are determined as a defective one, are marked by a letter “X.”
Afterwards, a process for cutting away the defective PCB units is performed by a routing machine in which information on a cutting location, a cutting shape, and a cutting length are programmed considering a shape, thickness, junction strength of the PCB units.
Next, nondefective PCB units are precisely aligned on portions, which are defined by removing the defective PCB units from the PCB panel, in response to the original pattern. Here, the nondefective units are obtained from another PCB panel or extra PCB units that are specially manufactured.
After the above, adhesive is injected into portions defined by removing the defective PCB units using the routing machine to bond the nondefective PCB units on the PCB panel in a state where a tape is attached on the PCB panel to prevent the adhesive from overflowing. As the adhesive, epoxy resin is generally used. The epoxy resin is injected by a programmed fixed-quantity by a quantitative epoxy injector.
Then, the PCB panel in which the epoxy is injected is transferred into a hot wind drier. When the epoxy is hardened in the hot wind drier, the PCB panel is withdrawn from the drier and inspected for its twist and deformation at a room temperature, after which the location of the replaced PCB units is inspected using a three-dimensional measuring device. In addition, the scratch of the PCB units and spread of the epoxy are further inspected by naked-eyes using a magnifier.
In order to easily mount parts on the cured PCB panel using an automatic machine without any work error, part insertion holes formed on the nondefective PCB units should be accurately aligned on relative locations on the PCB panel in response to a circuit design or Gerber data. Therefore, the bonding process should be performed after the nondefective PCB units for replacing the defective PCB units are accurately aligned on the PCB panel. With the goods minimized, the PCB panel is also minimized with a high density. Therefore, the more precision process for aligning the nondefective PCB units on a portion formed by removing the defective PCB units from the PCB panel is required.
FIGS. 1 to 3 show a perspective view illustrating a conventional method for aligning and bonding a nondefective PCB unit on the PCT panel. As shown in the drawings, a PCB panel and a nondefective PCB unit for replacing a defective PCB unit are inserted into a plurality of fixing pins installed on a flat-shaped jig for the location alignment of the nondefective PCB unit with respect to the PCB panel.
The method for replacing the defective PCB unit with the nondefective PCB unit will be briefly described hereinafter with reference to FIGS. 1 to 3.
In FIG. 1, there is shown a 4-array PCB panel 200 having four PCB units 201. When it is intended to replace a defective PCB unit 201a among the four PCB units 201 with a nondefective PCB unit 201b, portions in vicinity of bridges 202 that are connection portions for connecting the defect PCB unit 201a to the PCB panel are first cut away together with the bridges 202 as shown in FIG. 1, thereby removing the defective PCB unit 201a from the PCB panel. That is, the cut-away portions including the bridges are extended enough toward the PCB panel. The cutting shape is designed considering a shape and thickness of the PCB unit and strength of a bonding portion of the (nondefective) PCB unit. In addition to the shape shown in FIG. 1, a variety of other shapes including a shape shown in FIG. 3 can be also possible.
The PCB panel 200 from which the defective PCB unit 201a is removed and a nondefective PCB unit 201b for replacing the defective PCB unit 201 a are coupled on the jig 100.
The jig 100 is made of a Bakelite plate 101 on which a plurality of fixing pins 107 are forcibly embedded. The fixing pins 107 are inserted into fixing holes 203 formed on the PCB units 201 and the PCB panel 200, thereby realizing the location fixture of the PCB units 201 and the PCB panel 200. In this state, the nondefective PCB unit 201 b is fixed on a portion defined by removing the defective PCB unit 201a from the PCB panel 200. At this point, the fixing pins 107 formed on the jig 100 is also inserted into holes formed on the nondefective PCB unit 201b, thereby aligning the nondefective PCB unit 201b on a location where the defective PCB unit 201a has been originally located.
After aligning the nondefective PCB unit 201b, epoxy is injected into spaces between the nondefective PCB unit 201b and the PCB panel 200 and hardened, thereby bonding the nondefective PCB unit 201b on the PCB panel 200.
However, since the location aligning precision between the nondefective PCB unit 201b for replacing the defective PCB unit 201a and the PCB panel 200 depends on only the fixing pins on the jig, there is a limitation to obtain enough locating precision, as a result of which the yield of the cured PCB panel is deteriorated.
That is, in order to manufacture a precise jig, an expensive precise drilling machine for drilling the fixing pin insertion holes each having a precise diameter at a precise location is required. In addition, the fixing pins embedded in the jig should be also precisely processed. However, even when the fixing pins and the fixing pin insertion holes are precisely processed, there may be some errors during the embedding process of the fixing pins into the fixing pin insertion holes. Namely, it is difficult to manufacture the precise jig required for the high density PCB panel. Furthermore, the jig plate may be easily deformed and the locations of the pins are easily displaced, causing the defectiveness of the PCB panel. When the jig is deformed, the whole body of jig should be replaced, increasing the manufacturing costs.